Cytochrome c has been identified as an important participant in apoptosis. In living cells, cytochrome c is present in the intermembrane space of the mitochondria, where it plays a role in respiration. During apoptosis, however, cytochrome c translocates to the cytosol. Green et al. (1998) Cell 94:695-698; Martinou et al. (1999) Nature 399:411-412. Mitochondrial-produced reactive oxygen species (ROS) occur in bursts in the mitochondria and are involved in release of cytochrome c into the cytosol. Kirkland (2001) J. Neurosci 21(6):1949-1963. In the cytosol, cytochrome c binds to Apaf-1 in a dATP/ATP dependent manner, precipitating the oligomerization of Apaf-1. Kluck et al. (2000) J. Biol. Chem. 21:16127-16133. The ensuing recruitment and activation of caspase-9 results in the activation of further caspases, including caspase-3. These caspases in turn cleave many important substrates and orchestrate the final packaging of the apoptotic cell. Liu et al. (1997) Cell 89:175-184; Enari et al. (1998) Nature 391:43-50; Sahara (199) Nature 401:168-173.